I run a landscape business that has a mowing service. I have a list of customers that I pull into a table on the first of every month. The plan is to create invoice numbers for these customers. I will then use those invoice numbers for the month. At the end of the day we check off the customers that we visited, query those customers and add that info to the invoice detail table. At the end of the month the invoices are sent out and the process starts over.